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/*=============================================================================
Copyright (c) 2001-2015 Joel de Guzman
Copyright (c) 2015 Ahmed Charles
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
///////////////////////////////////////////////////////////////////////////////
//
// A Roman Numerals Parser (demonstrating the symbol table). This is
// discussed in the "Symbols" chapter in the Spirit User's Guide.
//
// [ JDG August 22, 2002 ] spirit1
// [ JDG March 13, 2007 ] spirit2
// [ JDG May 13, 2015 ] spirit X3
//
///////////////////////////////////////////////////////////////////////////////
#include <boost/config/warning_disable.hpp>
#include <boost/spirit/home/x3.hpp>
#include <iostream>
#include <string>
namespace client
{
namespace x3 = boost::spirit::x3;
namespace ascii = boost::spirit::x3::ascii;
///////////////////////////////////////////////////////////////////////////////
// Parse roman hundreds (100..900) numerals using the symbol table.
// Notice that the data associated with each slot is the parser's attribute
// (which is passed to attached semantic actions).
///////////////////////////////////////////////////////////////////////////////
struct hundreds_ : x3::symbols<unsigned>
{
hundreds_()
{
add
("C" , 100)
("CC" , 200)
("CCC" , 300)
("CD" , 400)
("D" , 500)
("DC" , 600)
("DCC" , 700)
("DCCC" , 800)
("CM" , 900)
;
}
} hundreds;
///////////////////////////////////////////////////////////////////////////////
// Parse roman tens (10..90) numerals using the symbol table.
///////////////////////////////////////////////////////////////////////////////
struct tens_ : x3::symbols<unsigned>
{
tens_()
{
add
("X" , 10)
("XX" , 20)
("XXX" , 30)
("XL" , 40)
("L" , 50)
("LX" , 60)
("LXX" , 70)
("LXXX" , 80)
("XC" , 90)
;
}
} tens;
///////////////////////////////////////////////////////////////////////////////
// Parse roman ones (1..9) numerals using the symbol table.
///////////////////////////////////////////////////////////////////////////////
struct ones_ : x3::symbols<unsigned>
{
ones_()
{
add
("I" , 1)
("II" , 2)
("III" , 3)
("IV" , 4)
("V" , 5)
("VI" , 6)
("VII" , 7)
("VIII" , 8)
("IX" , 9)
;
}
} ones;
///////////////////////////////////////////////////////////////////////////////
// roman (numerals) grammar
//
// Note the use of the || operator. The expression
// a || b reads match a or b and in sequence. Try
// defining the roman numerals grammar in YACC or
// PCCTS. Spirit rules! :-)
///////////////////////////////////////////////////////////////////////////////
namespace parser
{
using x3::eps;
using x3::lit;
using x3::_val;
using x3::_attr;
using ascii::char_;
auto set_zero = [](auto& ctx){ _val(ctx) = 0; };
auto add1000 = [](auto& ctx){ _val(ctx) += 1000; };
auto add = [](auto& ctx){ _val(ctx) += _attr(ctx); };
x3::rule<class roman, unsigned> const roman = "roman";
auto const roman_def =
eps [set_zero]
>>
(
-(+lit('M') [add1000])
>> -hundreds [add]
>> -tens [add]
>> -ones [add]
)
;
BOOST_SPIRIT_DEFINE(roman);
}
}
///////////////////////////////////////////////////////////////////////////////
// Main program
///////////////////////////////////////////////////////////////////////////////
int
main()
{
std::cout << "/////////////////////////////////////////////////////////\n\n";
std::cout << "\t\tRoman Numerals Parser\n\n";
std::cout << "/////////////////////////////////////////////////////////\n\n";
std::cout << "Type a Roman Numeral ...or [q or Q] to quit\n\n";
typedef std::string::const_iterator iterator_type;
using client::parser::roman; // Our parser
std::string str;
unsigned result;
while (std::getline(std::cin, str))
{
if (str.empty() || str[0] == 'q' || str[0] == 'Q')
break;
iterator_type iter = str.begin();
iterator_type const end = str.end();
bool r = parse(iter, end, roman, result);
if (r && iter == end)
{
std::cout << "-------------------------\n";
std::cout << "Parsing succeeded\n";
std::cout << "result = " << result << std::endl;
std::cout << "-------------------------\n";
}
else
{
std::string rest(iter, end);
std::cout << "-------------------------\n";
std::cout << "Parsing failed\n";
std::cout << "stopped at: \": " << rest << "\"\n";
std::cout << "-------------------------\n";
}
}
std::cout << "Bye... :-) \n\n";
return 0;
}
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